Method and apparatus for video coding

ABSTRACT

Method and decoder for reconstructing at least a sample of a block using an intra prediction angle determined from an intra prediction mode. The method includes decoding at least one syntax element from a coded video sequence. The at least one symax element is indicative of an intra prediction mode. An intra prediction angle is determined that corresponds to the indicated intra prediction mode based on a stored relationship between a plurality of intra prediction modes and a plurality of intra prediction angles. At least one sample of a block is reconstructed using the infra prediction angle that is determined to correspond to the indicated intra prediction mode. The plurality of intra prediction modes in the stored relationship can include at least one of a first plurality of wide angle prediction modes and a second plurality of wide angle prediction modes. The first plurality of wide angle prediction modes is beyond a bottom left direction diagonal mode and the second plurality of wide angle prediction modes is beyond a top right direction diagonal mode.

INCORPORATION BY REFERENCE

The present application is a continuation of and claims the benefit ofpriority to U.S. application Ser. No. 16/359,631, filed on Mar. 20,2019, which is a continuation of U.S. application Ser. No. 16/147,313(now U.S. Pat. No. 10,284,844), filed on Sep. 28, 2018, which claims thebenefit of priority to U.S. Provisional Application No. 62/711,390,“Improvements on Wide-Angle Intra Prediction” filed on Jul. 27, 2018,and 62/693,050, “Methods and Apparatus for Wide Angular Intra Predictionin Video Compression” filed on Jul. 2, 2018, the contents of each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reducing aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In Intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used in as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer bitsare required at a given quantization step size to represent the blockafter entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding/decoding of spatially neighboring, andpreceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is only using reference data from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode/submode/parameter combination can have an impactin the coding efficiency gain through intra prediction, and so can theentropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), benchmark set(BMS). A predictor block can be formed using neighboring samples valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstrearn or mayitself be predicted.

Referring to FIG. 1 , depicted in the lower right is a subset of ninepredictor directions known from the 35 possible predictor directions inH.265. The point where the arrows converge (101) represents the samplebeing predicted. The arrows represent the direction from which thesample is being predicted. For example, arrow (102) indicates thatsample (101) is predicted from a sample or samples to the upper right,at a 45 degree angle from the horizontal. Similarly, arrow (103)indicates that sample (101) is predicted from a sample or samples to thelower right of sample (101), in a 22.5 degree angle from the horizontal.

Still referring to FIG. 1 , on the top left there is depicted a squareblock (104) of 4×4 samples (indicated by a dashed, boldface line). Thesquare block (104) includes 16 samples, each labelled with an “s”, itsposition in Y dimension (e.g., row index) and its position in Xdimension (e.g., column index). For example, a sample S21 is the secondsample in Y dimensions (from the top) and the first (from the left)sample in X dimension. Similarly, a sample S44 is the fourth sample inthe block (104) in both Y and X dimension. As the block (104) is 4×4samples in size, the sample S44 is at the bottom right. Further shownare reference samples, that follow a similar numbering scheme. Areference sample is labelled with an R, its Y position (e.g., row index)and X position (column index) relative to the block (104). In both H.264and H.265, prediction samples neighbor the block under reconstruction;therefore no negative values need to be used.

Intra picture prediction can work by copying reference sample valuesfrom the neighboring samples as appropriated by the signaled predictiondirection. For example, assume the coded video bitstream includessignaling that, for this block, indicates a prediction directionconsistent with arrow (102)—that is, samples are predicted fromprediction sample or samples to the upper right, at a 45 degree anglefrom the horizontal. In that case, samples S41, S32, S23, and S14 arepredicted from same R05. Sample S44 is then predicted from R08.

In certain cases, the values of multiple reference samples may becombined, for example through interpolation, in order to calculate areference sample; especially when the directions are not evenlydivisible by 45 degrees.

The number of possible directions has increased as video codingtechnology developed. In H.264 (2003), nine different directions couldbe represented. That increased to 33 in H.265 (2013), and JEM/VVC/BMS,at the time of disclosure, can support up to 65 directions. Experimentshave been conducted to identify the most likely directions, and certaintechniques in the entropy coding are used to represent those likelydirections in a small number of bits, accepting a certain penalty forless likely directions. Further, the directions themselves can besometimes be predicted from neighboring directions used in neighboring,already decoded, blocks.

FIG. 2 is a schematic 201 that depicts 67 intra prediction modesaccording to JEM to illustrate the increasing number of predictiondirections over time.

The mapping of an intra prediction directions bits in the coded videobitstream that represent the direction can be different form videocoding technology to video coding technology; and can range, forexample, from simple direct mappings of prediction direction to intraprediction mode to codewords, to complex adaptive schemes involving mostprobably modes and similar techniques. A person skilled in the art isreadily familiar with those techniques. In all cases, however, there canbe certain directions that are statistically less likely to occur invideo content than certain other directions. As the goal of videocompression is the reduction of redundancy, those less likely directionswill, in a well working video coding technology, be represented by alarger number of bits than more likely directions.

SUMMARY

Aspects of the disclosure provide method and apparatus for video coding.In some examples, an apparatus includes receiving circuitry andprocessing circuitry.

One embodiment of the invention is directed to a method for videodecoding in a decoder. The method includes decoding at least one syntaxelement from a coded video sequence, the at least one syntax elementindicative of an intra prediction mode, determining an intra predictionangle that corresponds to the indicated intra prediction mode based on astored relationship between a plurality of intra prediction modes and aplurality of intra prediction angles, and reconstructing at least onesample of a block using the intra prediction angle that is determined tocorrespond to the indicated intra prediction mode. The plurality ofintra prediction modes in the stored relationship can include at leastone of a first plurality of wide angle prediction modes and a secondplurality of wide angle prediction modes. The first plurality of angleprediction modes is beyond a bottom left direction diagonal mode, andthe second plurality of angle prediction modes is beyond a top rightdirection diagonal mode. The relation may be stored as a look-up table.

Another embodiment of the invention is directed to a video decoder. Thedecoder includes processing circuitry configured to decode at least onesyntax element from a coded video sequence, the at least one syntaxelement indicative of an intra prediction mode, determine an intraprediction angle that corresponds to the indicated intra prediction modebased on a stored relationship between a plurality of intra predictionmodes and a plurality of intra prediction angles, and reconstruct atleast one sample of a block using the intra prediction angle that isdetermined to correspond to the indicated intra prediction mode. Theplurality of intra prediction modes in the stored relationship caninclude at least one of a first plurality of wide angle prediction modesand a second plurality of wide angle prediction modes. The firstplurality of angle prediction modes is beyond a bottom left directiondiagonal mode, and the second plurality of angle prediction modes isbeyond a top right direction diagonal mode. The decoder may store therelation as a look-up table.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video decoding cause the computer to perform the method forvideo coding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of exemplary intra prediction modes.

FIG. 2 is another illustration of exemplary intra prediction modes.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 7 is a block diagram of an encoder in accordance with anotherembodiment.

FIG. 8 is a block diagram of a decoder in accordance with anotherembodiment.

FIG. 9 is a diagram illustrating exemplary wide angle modes.

FIG. 10 is a diagram illustrating exemplary intra prediction angledefinition.

FIGS. 11A and 11B are diagrams of a method according to an embodiment ofthe invention.

FIG. 12 is a diagram illustrating prediction angles within and beyondthe diagonal directions.

FIG. 13 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 3 illustrates a simplified block diagram of a communication system300 according to an embodiment of the present disclosure. Thecommunication system 300 includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network 350. Forexample, the communication system 300 includes a first pair of terminaldevices 310 and 320 interconnected via the network 350. In the FIG. 3example, the first pair of terminal devices 310 and 320 performsunidirectional transmission of data. For example, the terminal device310 may code video data (e.g., a stream of video pictures that arecaptured by the terminal device 310) for transmission to the otherterminal device 320 via the network 350. The encoded video data can betransmitted in the form of one or more coded video bitstreams. Theterminal device 320 may receive the coded video data from the network350, decode the coded video data to recover the video pictures anddisplay video pictures according to the recovered video data.Unidirectional data transmission may be common in media servingapplications and the like.

In another example, the communication system 300 includes a second pairof terminal devices 330 and 340 that performs bidirectional transmissionof coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices 330 and 340 maycode video data (e.g., a stream of video pictures that are captured bythe terminal device) for transmission to the other terminal device ofthe terminal devices 330 and 340 via the network 350. Each terminaldevice of the terminal devices 330 and 340 also may receive the codedvideo data transmitted by the other terminal device of the terminaldevices 330 and 340, and may decode the coded video data to recover thevideo pictures and may display video pictures at an accessible displaydevice according to the recovered video data.

In the FIG. 3 example, the terminal devices 310, 320, 330 and 340 may beillustrated as servers, personal computers and smart phones but theprinciples of the present disclosure may be not so limited. Embodimentsof the present disclosure find application with laptop computers, tabletcomputers, media players and/or dedicated video conferencing equipment.The network 350 represents any number of networks that convey codedvideo data among the terminal devices 310, 320, 330 and 340, includingfor example wireline (wired) and/or wireless communication networks. Thecommunication network 350 may exchange data in circuit-switched and/orpacket-switched channels. Representative networks includetelecommunications networks, local area networks, wide area networksand/or the Internet. For the purposes of the present discussion, thearchitecture and topology of the network 350 may be immaterial to theoperation of the present disclosure unless explained herein below.

FIG. 4 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem 413, that can includea video source 401, for example a digital camera, creating for example astream of video pictures 402 that are uncompressed. In an example, thestream of video pictures 402 includes samples that are taken by thedigital camera. The stream of video pictures 402, depicted as a boldline to emphasize a high data volume when compared to encoded video data404 (or coded video bitstreams), can be processed by an electronicdevice 420 that includes a video encoder 403 coupled to the video source401. The video encoder 403 can include hardware, software, or acombination thereof to enable or implement aspects of the disclosedsubject matter as described in more detail below. The encoded video data404 (or encoded video bitstream 404), depicted as a thin line toemphasize the lower data volume when compared to the stream of videopictures 402, can be stored on a streaming server 405 for future use.One or more streaming client subsystems, such as client subsystems 406and 408 in FIG. 4 can access the streaming server 405 to retrieve copies407 and 409 of the encoded video data 404. A client subsystem 406 caninclude a video decoder 410, for example, in an electronic device 430.The video decoder 410 decodes the incoming copy 407 of the encoded videodata and creates an outgoing stream of video pictures 411 that can berendered on a display 412 (e.g., display screen) or other renderingdevice (not depicted). In some streaming systems, the encoded video data404, 407, and 409 (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Codingor VVC. The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices 420 and 430 can include othercomponents (not shown). For example, the electronic device 420 caninclude a video decoder (not shown) and the electronic device 430 caninclude a video encoder (not shown) as well.

FIG. 5 shows a block diagram of a video decoder 510 according to anembodiment of the present disclosure. The video decoder 510 can beincluded in an electronic device 530. The electronic device 530 caninclude a receiver 531 (e.g., receiving circuitry). The video decoder510 can be used in the place of the video decoder 410 in the FIG. 4example.

The receiver 531 may receive one or more coded video sequences to bedecoded by the video decoder 510; in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel 501, which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver 531 may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver 531 may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory 515 may be coupled inbetween the receiver 531 and an entropy decoder/parser 520 (“parser 520”henceforth). In certain applications, the buffer memory 515 is part ofthe video decoder 510. In others, it can be outside of the video decoder510 (not depicted). In still others, there can be a buffer memory (notdepicted) outside of the video decoder 510, for example to combatnetwork jitter, and in addition another buffer memory 515 inside thevideo decoder 510, for example to handle playout timing. When thereceiver 531 is receiving data from a store/forward device of sufficientbandwidth and controllability, or from an isosynchronous network, thebuffer memory 515 may not be needed, or can be small. For use on besteffort packet networks such as the Internet, the buffer memory 515 maybe required, can be comparatively large and can be advantageously ofadaptive size, and may at least partially be implemented in an operatingsystem or similar elements (not depicted) outside of the video decoder510.

The video decoder 510 may include the parser 520 to reconstruct symbols521 from the coded video sequence. Categories of those symbols includeinformation used to manage operation of the video decoder 510, andpotentially information to control a rendering device such as a renderdevice 512 (e.g., a display screen) that is not an integral part of theelectronic device 530 but can be coupled to the electronic device 540,as is shown in FIG. 5 . The control information for the renderingdevice(s) may be in the form of Supplementary Enhancement Information(SEI messages) or Video Usability Information (VUI) parameter setfragments (not depicted). The parser 520 may parse/entropy-decode thecoded video sequence that is received. The coding of the coded videosequence can be in accordance with a video coding technology orstandard, and can follow various principles, including variable lengthcoding, Huffman coding, arithmetic coding with or without contextsensitivity, and so forth. The parser 520 may extract from the codedvideo sequence, a set of subgroup parameters for at least one of thesubgroups of pixels in the video decoder, based upon at least oneparameter corresponding to the group. Subgroups can include Groups ofPictures (GOPs) pictures, tiles, slices, macroblocks, Coding Units(CUs), blocks, Transform Units (TUs), Prediction Units (PUs) and soforth. The parser 520 may also extract from the coded video sequenceinformation such as transform coefficients, quantizer parameter values,motion vectors, and so forth.

The parser 520 may perform entropy decoding/parsing operation on thevideo sequence received from the buffer memory 515, so as to createsymbols 521.

Reconstruction of the symbols 521 can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser 520. The flow of such subgroup control information between theparser 520 and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder 510can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit 551. Thescaler/inverse transform unit 551 receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc., as symbol(s) 521 from the parser 520. The scaler/inverse transformunit 551 can output blocks comprising sample values, that can be inputinto aggregator 555.

In some cases, the output samples of the scaler/inverse transform 551can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit 552. In some cases, the intra picture predictionunit 552 generates a block of the same size and shape of the block underreconstruction, using surrounding already reconstructed informationfetched from the current picture buffer 558. The current picture buffer558 buffers, for example, partly reconstructed current picture and/orfully reconstructed current picture. The aggregator 555, in some cases,adds, on a per sample basis, the prediction information the intraprediction unit 552 has generated to the output sample information asprovided by the scaler/inverse transform unit 551.

In other cases, the output samples of the sealer/inverse transform unit551 can pertain to an inter-coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit 553 canaccess reference picture memory 557 to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols 521 pertaining to the block, these samples can be addedby the aggregator 555 to the output of the scaler/inverse transform unit551 (in this case called the residual samples or residual signal) so asto generate output sample information. The addresses within thereference picture memory 557 from where the motion compensationprediction unit 553 fetches prediction samples can be controlled bymotion vectors, available to the motion compensation prediction unit 553in the form of symbols 521 that can have, for example X, Y, andreference picture components. Motion compensation also can includeinterpolation of sample values as fetched from the reference picturememory 557 when sub-sample exact motion vectors are in use, motionvector prediction mechanisms, and so forth.

In other cases, the output samples of the scaler/inverse transform unit551 can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit 553 canaccess reference picture memory 557 to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols 521 pertaining to the block, these samples can be addedby the aggregator 555 to the output of the scaler/inverse transform unit551 (in this case called the residual samples or residual signal) so asto generate output sample information. The addresses within thereference picture memory 557 from where the motion compensationprediction unit 553 fetches prediction samples can be controlled bymotion vectors, available to the motion compensation prediction unit 553in the form of symbols 521 that can have, for example X, Y, andreference picture components. Motion compensation also can includeinterpolation of sample values as fetched from the reference picturememory 557 when sub-sample exact motion vectors are in use, motionvector prediction mechanisms, and so forth.

The output samples of the aggregator 555 can be subject to various loopfiltering techniques in the loop filter unit 556. Video compressiontechnologies can include in-loop filter technologies that are controlledby parameters included in the coded video sequence (also referred to ascoded video bitstream) and made available to the loop filter unit 556 assymbols 521 from the parser 520, but can also be responsive tometa-information obtained during the decoding of previous (in decodingorder) parts of the coded picture or coded video sequence, as well asresponsive to previously reconstructed and loop-filtered sample values.

The output of the loop filter unit 556 can be a sample stream that canbe output to the render device 512 as well as stored in the referencepicture memory 557 for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser 520), the current picture buffer 558 can become apart of the reference picture memory 557, and a fresh current picturebuffer can be reallocated before commencing the reconstruction of thefollowing coded picture.

The video decoder 510 may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as document in thevideo compression technology or standard. Specifically, a profile canselect a certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver 531 may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder 510 to properly decode the data and/or to more accuratelyreconstruct the original video data. Additional data can be in the formof, for example, temporal, spatial, or signal noise ratio (SNR)enhancement layers, redundant slices, redundant pictures, forward errorcorrection codes, and so on.

FIG. 6 shows a block diagram of a video encoder 603 according to anembodiment of the present disclosure. The video encoder 603 is includedin an electronic device 620. The electronic device 620 includes atransmitter 640 (e.g., transmitting circuitry). The video encoder 603can be used in the place of the video encoder 403 in the FIG. 4 example.

The video encoder 603 may receive video samples from a video source 601(that is not part of the electronic device 420 in the FIG. 4 example)that may capture video image(s) to be coded by the video encoder 603. Inanother example, the video source 601 is a part of the electronic device620.

The video source 601 may provide the source video sequence to be codedby the video encoder 603 in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . )and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source 601 may be a storagedevice storing previously prepared video. In a videoconferencing system,the video source 601 may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc, in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder 603 may code and compressthe pictures of the source video sequence into a coded video sequence643 in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function of acontroller 650. In some embodiments, the controller 650 controls otherfunctional units as described below and is functionally coupled to theother functional units. The coupling is not depicted for clarity.Parameters set by the controller 650 can include rate control relatedparameters (picture skip, quantizer, lambda value of rate-distortionoptimization techniques, . . . ), picture size, group of pictures (GOP)layout, maximum motion vector search range, and so forth. The controller650 can be configured to have other suitable functions that pertain tothe video encoder 603 optimized for a certain system design.

In some embodiments, the video encoder 603 is configured to operate in acoding loop. As an oversimplified description, in an example, the codingloop can include a source coder 630 (e.g., responsible for creatingsymbols, such as a symbol stream, based on an input picture to be coded,and a reference picture(s)), and a (local) decoder 633 embedded in thevideo encoder 603. The decoder 633 reconstructs the symbols to createthe sample data in a similar manner as a (remote) decoder also wouldcreate (as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). The reconstructed sample stream (sample data)is input to the reference picture memory 634. As the decoding of asymbol stream leads to bit-exact results independent of decoder location(local or remote), the content in the reference picture memory 634 isalso bit exact between the local encoder and remote encoder. In otherwords, the prediction part of an encoder “sees” as reference picturesamples exactly the same sample values as a decoder would “see” whenusing prediction during decoding. This fundamental principle ofreference picture synchronicity (and resulting drift, if synchronicitycannot be maintained, for example because of channel errors) is used insome related arts as well.

The operation of the “local” decoder 333 can be the same as of a“remote” decoder, such as the video decoder 610, which has already beendescribed in detail above in conjunction with FIG. 5 . Briefly referringalso to FIG. 5 , however, as symbols are available and encoding/decodingof symbols to a coded video sequence by an entropy coder 545 and theparser 520 can be lossless, the entropy decoding parts of the videodecoder 510, including the buffer memory 515, and parser 520 may not befully implemented in the local decoder 633.

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder 630 may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously-coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine 632 codes differences between pixel blocks ofan input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder 633 may decode coded video data of pictures thatmay be designated as reference pictures, based on symbols created by thesource coder 630. Operations of the coding engine 632 may advantageouslybe lossy processes. When the coded video data may be decoded at a videodecoder (not shown in FIG. 6 ), the reconstructed video sequencetypically may be a replica of the source video sequence with someerrors. The local video decoder 633 replicates decoding processes thatmay be performed by the video decoder on reference pictures and maycause reconstructed reference pictures to be stored in the referencepicture cache 634. In this manner, the video encoder 603 may storecopies of reconstructed reference pictures locally that have commoncontent as the reconstructed reference pictures that will be obtained bya far-end video decoder (absent transmission errors).

The predictor 635 may perform prediction searches for the coding engine632. That is, for a new picture to be coded, the predictor 635 maysearch the reference picture memory 634 for sample data (as candidatereference pixel blocks) or certain metadata such as reference picturemotion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor 635may operate on a sample block-by-pixel block basis to find appropriateprediction references. In some cases, as determined by search resultsobtained by the predictor 635, an input picture may have predictionreferences drawn from multiple reference pictures stored in thereference picture memory 634.

The controller 650 may manage coding operations of the source coder 630,including, for example, setting of parameters and subgroup parametersused for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder 645. The entropy coder 645translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter 640 may buffer the coded video sequence(s) as created bythe entropy coder 645 to prepare for transmission via a communicationchannel 660, which may be a hardware/software link to a storage devicewhich would store the encoded video data. The transmitter 640 may mergecoded video data from the video coder 603 with other data to betransmitted, for example, coded audio data and/or ancillary data streams(sources not shown).

The controller 650 may manage operation of the video encoder 603. Duringcoding, the controller 650 may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of Intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder 603 may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder 603 may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter 640 may transmit additional data withthe encoded video. The source coder 630 may include such data as part ofthe coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to Intra prediction) makes uses of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first and a second reference picture thatare both prior in decoding order to the current picture in the video(but may be in the past and future, respectively, in display order) areused. A block in the current picture can be coded by a first motionvector that points to a first reference block in the first referencepicture, and a second motion vector that points to a second referenceblock in the second reference picture. The block can be predicted by acombination of the first reference block and the second reference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC (High EfficiencyVideo Coding) standard, a picture in a sequence of video pictures ispartitioned into coding tree units (CTU) for compression, the CTUs in apicture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16pixels. In general, a CTU includes three coding tree blocks (CTBs),which are one luma CTB and two chroma CTBs. Each CTU can be recursivelyquadtree split into one or multiple coding units (CUs). For example, aCTU of 64×64 pixels can be split into one CU of 64×64 pixels, or 4 CUsof 32×32 pixels, or 16 CUs of 16×16 pixels. In an example, each CU isanalyzed to determine a prediction type for the CU, such as an interprediction type or an intra prediction type. The CU is split into one ormore prediction units (PUs) depending on the temporal and/or spatialpredictability. Generally, each PU includes a luma prediction block(PB), and two chroma PBs. In an embodiment, a prediction operation incoding (encoding/decoding) is performed in the unit of a predictionblock. Using a luma prediction block as an example of a predictionblock, the prediction block includes a matrix of values (e.g., lumavalues) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8pixels and the like.

FIG. 7 shows a diagram of a video encoder 703 according to anotherembodiment of the disclosure. The video encoder 703 is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder 703 is used in theplace of the video encoder 403 in the FIG. 4 example.

In an HEVC example, the video encoder 703 receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder 703 determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder 703 may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder703 may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder 703 includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 7 example, the video encoder 703 includes the inter encoder730, an intra encoder 722, a residue calculator 723, a switch 726, aresidue encoder 724, a general controller 721 and an entropy encoder 725coupled together as shown in FIG. 7 .

The inter encoder 730 is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique.

The intra encoder 722 is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform and, in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques).

The general controller 721 is configured to determine general controldata and control other components of the video encoder 703 based on thegeneral control data. In an example, the general controller 721determines the mode of the block, and provides a control signal to theswitch 726 based on the mode. For example, when the mode is the intra,the general controller 721 controls the switch 726 to select the intramode result for use by the residue calculator 723, and controls theentropy encoder 725 to select the intra prediction information andinclude the intra prediction information in the bitstream; and when themode is the inter mode, the general controller 721 controls the switch726 to select the inter prediction result for use by the residuecalculator 723, and controls the entropy encoder 725 to select the interprediction information and include the inter prediction information inthe bitstream.

The residue calculator 723 is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder 722 or the inter encoder 730. Theresidue encoder 724 is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder 724 is configured to convert the residuedata in the frequency domain, and generate the transform coefficients.The transform coefficients are then subject to quantization processingto obtain quantized transform coefficients.

The entropy encoder 725 is configured to format the bitstream to includethe encoded block. The entropy encoder 725 is configured to includevarious information according to a suitable standard, such as HEVCstandard. In an example, the entropy encoder 725 is configured toinclude the general control data, the selected prediction information(e.g., intra prediction information or inter prediction information),the residue information, and other suitable information in thebitstream. Note that, according to the disclosed subject matter, whencoding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 8 shows a diagram of a video decoder 810 according to anotherembodiment of the disclosure. The video decoder 810 is configured toreceive a coded pictures that are part of a coded video sequence, anddecode the coded picture to generate a reconstructed picture. In anexample, the video decoder 810 is used in the place of the video decoder410 in the FIG. 4 example.

In the FIG. 8 example, the video decoder 810 includes an entropy decoder871, an inter decoder 880, a residue decoder 873, a reconstructionmodule 874, and an intra decoder 872 coupled together as shown in FIG. 8.

The entropy decoder 871 can be configured to reconstruct, from the codedpicture, certain symbols that represent the syntax elements of which thecoded picture made up. Such symbols can include, for example, the modein which a block is coded (such as, for example, intra, inter,b-predicted, the latter two in merge submode or another submode),prediction information (such as, for example, intra predictioninformation or inter prediction information) that can identify certainsample or metadata that is used for prediction by the intra decoder 872or the inter decoder 880 respectively residual information in the formof, for example, quantized transform coefficients, and the like. In anexample, when the prediction mode is inter or bi-predicted mode, theinter prediction information is provided to the inter decoder 880; andwhen the prediction type is the intra prediction type, the intraprediction information is provided to the intra decoder 872. Theresidual information can be subject to inverse quantization and isprovided to the residue decoder 873.

The inter decoder 880 is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder 872 is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder 873 is configured to perform inverse quantization toextract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder 873 may alsorequire certain control information (to include the Quantizer ParameterQP), and that information may be provided by the entropy decoder 871(datapath not depicted as this may be low volume control informationonly).

The reconstruction module 874 is configured to combine, in the spatialdomain, the residual as output by the residue decoder 873 and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders 403, 603 and 703, and the videodecoders 410, 510 and 810 can be implemented using any suitabletechnique. In an embodiment, the video encoders 403, 603 and 703, andthe video decoders 410, 510 and 810 can be implemented using one or moreintegrated circuits. In another embodiment, the video encoders 403, 603and 703, and the video decoders 410, 510 and 810 can be implementedusing one or more processors that execute software instructions.

In the decoding method according to a first embodiment of thedisclosure, wide angles beyond the range of prediction directionscovered by conventional intra prediction modes are used, which arecalled wide angular intra prediction modes. These wide angles are onlyapplied for non-square blocks. Angles going beyond 45 degree in thetop-right direction (intra prediction mode 34 in HEVC) are used if theblock width is larger than block height. Angles going beyond 45 degreein the bottom-left direction (intra prediction mode 2 in HEVC) are usedif the block height is larger than block width. Mode 2 is referred to asthe bottom-left diagonal mode and Mode 34 is referred to as thetop-right diagonal mode when 35 HEVC intra prediction modes are applied.

As described in U.S. Provisional Application Nos. 62/679,664,62/693,050, 62/693,046, which are incorporated herein by reference intheir entirety, for non-square blocks, several conventional angularintra prediction modes are replaced with wide angular modes. Thereplaced modes are signaled using the original method and remapped tothe indices of wide angular modes after parsing. The total number ofintra prediction modes is unchanged, i.e., 35 as in VVC Test Model(VTM)-1.0, or 67 as in BMS-1.0, and the intra mode coding is unchanged.

In the case of 35 intra prediction modes, the replaced intra predictionmodes are illustrated in below Table 1.

TABLE 1 Condition Replaced intra prediction modes W/H == 2 Modes 2, 3, 4W/H < 2 Modes 2, 3, 4, 5, 6 W/H == 1 None H/W == 1/2 Modes 32, 33, 34H/W < 1/2 Modes 30, 31, 32, 33, 34

In the case of 67 intra prediction modes, the replaced intra predictionmodes are illustrated in below Table 2.

TABLE 2 Condition Replaced intra prediction modes W/H == 2 Modes 2, 3,4, 5, 6, 7 W/H > 2 Modes 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 W/H == 1 NoneH/W == 1/2 Modes 61, 62, 63, 64, 65, 66 H/W < 1/2 Mode 57, 58, 59, 60,61, 62, 63, 64, 65,66

As indicated in Table 2, up to 10 modes are replaced by wide angle modesbeyond the diagonal directions.

FIG. 9 shows an example of how angular intra modes are replaced withwide angular modes for non-square blocks. In this example, mode 2 andmode 3 are replaced with wide angle mode 35 and mode 36, respectively,where the direction of mode 35 is pointing to the opposite direction ofmode 3, and the direction of mode 36 is pointing to the oppositedirection of mode 4.

An intra sample substitution process is used in HEVC. The intra samplesubstitution process of intra mode is described in below, which includesreference sample substitution process, filtering process of neighboringprocess, and intra prediction process.

Inputs to this process are:

-   -   reference samples p[x][y] with x=−1, y=−1..nTbS*2−1 and        x=0..nTbS*2−1, y=−1 for intra sample prediction, a transform        block size nTbS, a variable cIdx specifying the color component        of the current block.

Outputs of this process are the modified reference samples p[x][y] withx=−1, y=−1..nTbS*2−1 and x=0..nTbS*2−1, y=−1 for intra sampleprediction.

The variable bitDepth is derived as follows:

-   -   If cIdx is equal to 0, bitDepth is set equal to BitDepthY.    -   Otherwise, bitDepth is set equal to BitDepthC.

The values of the samples p[x][y] with x=−1, y=−1..nTbS*2−1 andx=0..nTbS*2−1, y=−1 are modified as follows:

-   -   If all samples p[x][y] with x=−1, y=−1..nTbS*2−1 and        x=0..nTbS*2−1, y=−1 are marked as “not available for intra        prediction”, the value 1<<(bitDepth−1) is substituted for the        values of all samples p[x][y].    -   Otherwise (at least one but not all samples 9[x][y] are marked        as “not available for intra prediction”), the following ordered        steps are performed:        -   1. When p[−1][nTbS*2−1] is marked as “not available for            intra prediction”, search sequentially starting from x=−1,            y=nTbS*2−1 to x=−1, y=−1, then from x=0, y=−1 to x=nTbS*2−1,            y=−1. Once a sample p[x][y] marked as “available for intra            prediction” is found, the search is terminated and the value            of p[x][y] is assigned to p[−1][nTbS*2−1].        -   2. Search sequentially starting from x=−1, y=nTbS*2−2 to            x=−1, y=−1, when p[x][y] is marked as “not available for            intra prediction”, the value of p[x][y+1] is substituted for            the value of p[x][y].        -   3. For x=0..nTbS*2−1, y=−1, when p[x][y] is marked as “not            available for intra prediction”, the value of p[x−1][y] is            substituted for the value of p[x][y].

All samples p[x][y] with x=−1, y=−1..nTbS*2−1 and x=0..nTbS*2−1, y=−1are marked as “available for intra prediction”.

Neighboring samples are filtered. Inputs to this process are as follows:

-   -   the neighboring samples p[x][y], with x=−1, y=−1..nTbS*2−1 and        x=0..nTbS*2−1, y=−1,        -   a variable nTbS specifying the transform block size.

Outputs of this process are the filtered samples pF[x][y], with x=−1,y=−1..nTbS*2−1 and x=0..nTbS*2−1, y=−1. The variable filterFlag isderived as follows:

-   -   If one or more of the following conditions are true, filterFlag        is set equal to 0:        -   predModeIntra is equal to INTRA_DC,        -   nTbS is equal 4.    -   Otherwise, the following applies:        -   The variable minDistVerHor is set equal to            Min(Abs(predModeIntra−26). Abs(predModeIntra−10)).        -   The variable intraHorVerDistThres[nTbS] is specified in            Table 8 3.        -   The variable filterFlag is derived as follows:            -   If minDistVerHor is greater than                intraHorVerDistThres[nTbS], filterFlag is set equal to                1.            -   Otherwise, filterFlag is set equal to 0.

Table 3 below specifies intraHorVertDistThres[nTbbS] for varioustransform block sizes.

TABLE 3 nTbS = 8 nTbS = 16 nTbS = 32 intraHorVerDistThres[nTbS] 7 1 0

When filterFlag is equal to 1, the following applies:

-   -   The variable biIntFlag is derived as follows:        -   If all of the following conditions are true, biIntFlag is            set equal to 1:            -   strong_intra_smoothing_enabled_flag is equal to 1            -   nTbS is equal to 32            -   Abs(p[−1][−1]+p[nTbS*2−1][−1]−2*p[nTbS−1][−1])<(1<<(BitDepthY−5))            -   Abs(p[−1][−1]+p[−1][nTbS*2−1]−2*p[−1][nTbS−1])<(1<<(BitDepthY−5))        -   Otherwise, biIntFlag is set equal to 0.    -   The filtering is performed as follows:        -   If biIntFlag is equal to 1, the filtered sample values            pF[x][y] with x=−1, y=−1..63 and x=0..63, y=−1 are derived            as follows:    -   pF[−1][−1]=p[−1][−1]    -   pF[−1][y]=((63−y)*p[−1][−1]+(y+1)*p[−1][63]+32)>>6 for y=0..62        (8-31)    -   pF[−1][63]=p[−1][63]    -   pF[x][−1]=((63−x)*p[−1][−1]+(x+1)*p[63][−1]+32)>>6 for x=0..62        (8-33)    -   pF[63][−1]=p[63][−1]        -   Otherwise (biIntFlag is equal to 0), the filtered sample            values pF[x][y] with x=−1, y=−1..nTbS*2−1 and x=0..nTbS*2−1,            y=−1 are derived as follows:    -   pF[−1][−1]=(p[−1][0]+2*p[−1][−1]+p[0][−1]+2)>>2    -   pF[−1][y]=(p[−1][y+1]+2*p[−1][y]+p[−1][y−1]+2)>>2 for        y=0..nTbs*2−2    -   pF[−1][nTbS*2−1]=p[−1][nTbS*2−1]    -   pF[x][−1]=(p[x−1][−1]+2*p[x][−1]+p[x+1][−1]+2)>>2 for        x=0..nTbS*2−2    -   pF[nTbS*2−1][−1]=p[nTbS*2−1][−1]

The intra prediction mode is specified in the range of INTRA_ANGULAR2 toINTRA_ANGULAR34. Inputs to this process are

-   -   the intra prediction mode predModeIntra,    -   the neighboring samples p[x][y], with x=−1, y=−1..nTbS*2−1 and        x=0..nTbS*2−1, y=−1,    -   a variable nTbS specifying the transform block size, and    -   a variable cIdx specifying the color component of the current        block.

Outputs of this process are the predicted samples predSamples[x][y],with x, y=0..nTbS−1.

FIG. 10 illustrates the 33 intra angles and Table 4 specifies themapping between predModeIntra (pMI) and the angle parameterintraPredAngle (iPA).

TABLE 4 pMI 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 iPA — 32 36 21 1713 9 5 2 0 −2 −5 −9 −13 −17 −21 −26 pMI 18 19 20 21 22 23 24 25 26 27 2829 30 31 32 33 34 iPA −32 −26 −21 −17 −13 −9 −5 −2 0 2 5 9 13 17 21 2632As illustrated by FIG. 10 , the intraPredAngle is a value indicating apredetermined distance measure from the vertical or horizontal mode. Asmaller absolute value of intraPredAngle indicates a smaller distance tothe vertical or horizontal mode.

Table 5 specifies the relationship between predModeIntra and the inverseangle parameter invAngle.

TABLE 5 predModeIntra 11 12 13 14 15 16 17 18 invAngle −4096 −1638 −910−630 −482 −390 −315 −256 predModeIntra 19 20 21 22 23 24 25 26 invAngle−315 −390 −482 −630 −910 −1638 −4096 —

The values of the prediction samples predSamples[x][y], with x,y=0..nTbS−1 are derived as follows:

-   -   If predModeIntra is equal or greater than 18, the following        ordered steps apply:        -   1. The reference sample array ref[x] is specified as            follows:            -   ref[x]=p[−1+x][−1], with x=0..nTbS            -   If intraPredAngle is less than 0, the main reference                sample array is extended as follows:        -    When (nTbS*intraPredAngle)>>5 is less than −1,            ref[x]=p[−1][−1((x*invAngle+128)>>8)], with            x=−1..(nTbS*intraPredAngle)>>5.            -   Otherwise, ref[x]=p[−1+x][−1], with x=nTbS+1..2*nTbS.        -   2. The values of the prediction samples predSamples[x][y],            with x, y=0..nTbS−1 are derived as follows:            -   a. The index variable iIdx and the multiplication factor                iFact are derived as follows:                -   iIdx=((y+1)*intraPredAngle)>>5                -   iFact=((y+1)*(intraPredAngle) & 31            -   b. Depending on the value of iFact, the following                applies:                -   If iFact is not equal to 0, the value of the                    prediction samples predSamples[x][y] is derived as                    follows:                -    predSamples[x][y]=((32−iFact)*ref[x+iIdx+1]+iFact*ref[x+iIdx+2]+16)>>5                -   Otherwise, the value of the prediction samples                    predSamples[x][y] is derived as follows:                -    predSamples[x][y]=ref[x+iIdx+1]            -   c. When predModeIntra is equal to 26 (vertical), cIdx is                equal to 0 and nTbS is less than 32, the following                filtering applies with x=0, y=0..nTbS−1:            -    predSamples[x][y]=Clip1Y(p[x][−1]+((p[−1][y]−p[−1][−1])>>1)),    -   Otherwise (predModeIntra is less than 18), the following ordered        steps apply:        -   1. The reference sample array ref[x] is specified as            follows:            -   The following applies:                -   ref[x]=p[−1][−1+x], with x=0..nTbS            -   If intraPredAngle is less than 0, the main reference                sample array is extended as follows:            -    When (nTbS*intraPredAngle)>>5 is less than −1,                -   ref[x]=p[−1+((x*invAngle+128)>>8)][−1],                -    with x=−1..(nTbS*intraPredAngle)>>5            -   Otherwise,                -   ref[x]=p[−1][−1+x], with x=nTbS+1..2*nTbS        -   2. The values of the prediction samples predSamples[x][y],            with x, y=0..nTbS−1 are derived as follows:        -   a. The index variable iIdx and the multiplication factor            iFact are derived as follows:            -   iIdx=((x+1)*intraPredAngle)>>5            -   iFact=((x+1)*intraPredAngle) & 31        -   b. Depending on the value of iFact, the following applies:        -   If iFact is not equal to 0, the value of the prediction            samples predSamples[x][y] is derived as follows:            -   predSamples[x][y]=((32−iFact)*ref[y+iIdx+1]+iFact*ref[y+iIdx+2]+16)>>5            -   Otherwise, the value of the prediction samples                predSamples[x][y] is derived as follows:            -   predSamples[x][y]=ref[y+iIdx+1]        -   c. When predModeIntra is equal to 10 (horizontal), cIdx is            equal to 0 and nTbS is less than 32, the following filtering            applies with x=0..nTbS−1, y=0:    -   predSamples[x][y]=Clip1Y(p[−1][y]+((p[x][−1]−p[−1][−1])>>1)).

In the first embodiment of the method of decoding according to thedisclosure shown in FIGS. 11A and 11B, wide angle modes are included inspecifying the relationship between predModeIntra and intraPredAngle. Upto ten additional wide angle modes are added beyond the diagonaldirections. The relationship is specified as set forth in Table 6 whichmay be implemented as a lookup table.

TABLE 6 pMI −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 0 1 2 3 4 5 6 IPA 114 93 7968 60 54 49 45 39 35 — — 32 29 26 23 21 pMI 7 8 9 10 11 12 13 14 15 1617 18 19 20 21 22 23 iPA 19 17 15 13 11  9 7 5 3 2 1 0 −1 −2 −3 −5 −7pMI 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 iPA −9 −11 −13−25 −17 −19 −21 −23 −26 −29 −32 −29 −26 −23 −21 −19 −17 pMI 41 42 43 4445 46 47 48 49 50 51 52 53 54 55 56 57 iPA −15 −13 −11 −9 −7 −5 −3 −2 −10 1 2 3 5 7 9 11 pMI 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74iPA 13 15 17 19 21 23 26 29 32 35 39 45 49 54 60 68 79 pMI 75 76 iPA 93114

The ten intra modes below 0 are indicated as −1 to −10 while the tenmodes above 66 are indicated as 67-76. The values for the added anglesrange from 35 to 114.

In step 1100, one or more syntax elements are decoded from a videosequence. In the example of FIG. 8 , entropy decoder 871 decodes certainsymbols that represent the syntax elements of which the coded picture ismade up from a coded video sequence. Intra decoder 872 produces aprediction result. Such symbols can include, for example, predictioninformation and the intra prediction mode can be determined. From therelationship shown in Table 6, the intra prediction angle is determinedfrom the intra prediction mode (Step 1101). A sample of the block isreconstructed using the determined intra prediction angle (Step 1102).For example, the reconstruction module 874 reconstructs the sample ofthe block.

The relationship between the intra prediction angle and the intraprediction mode can be stored in a look up table (step 1110), forexample in the reconstruction module 874. The intra prediction angle canbe determined from the look up table using the determined intraprediction mode (step 1111).

The method can be applied to reconstructing at least one sample of anon-square block and square blocks using the relationship between theintra prediction mode and the intra prediction angle. The non-squareblocks use the wide angle modes.

In further embodiment of the method according to the disclosure, thepredModeIntra and intraPredAngle values are modified. In these furtherembodiments, the block height is given as TbW and the block width isgiven as TbH. In a second embodiment, the values of predModeIntra andwideAngle are modified as follows:

-   -   If nTbW>nTbH and intraPredAngle>((32*nTbH/nTbW)+1) and        predModeIntra<34        -   If intraPredAngle>9, predModeIntra=predModeIntra+65, and            intra smoothing is performed;        -   Otherwise, predModeIntra=66,    -   If nTbH>nTbW and intraPredAngle>((32*nTbW/nTbH)+1) and        predModeIntra>34        -   If intraPredAngle>9, predModeIntra=predModeIntra−67, and            intra smoothing is performed;        -   Otherwise, predModeIntra=2.

In a third embodiment, the values of predModeIntra and wideAngle aremodified as follows:

-   -   If nTbW>nTbH and intraPredAngle>((32*nTbH/nTbW)+1) and        predModeIntra<34        -   If intraPredAngle>9, predModeIntra=predModeIntra+65, and            intra smoothing is performed;        -   Otherwise, predModeIntra=68−predModeIntra,    -   If nTbH>nTbW and intraPredAngle>((32*nTbW/nTbH)+1) and        predModeIntra>34        -   If intraPredAngle>9, predModeIntra=predModeIntra−67, and            intra smoothing is performed;        -   Otherwise, predModeIntra=68−predModeIntra.

In a fourth embodiment, the values of predModeIntra and wideAngle aremodified as follows:

-   -   If nTbW>nTbH and intraPredAngle>((32*nTbH/nTbW)+1) and        predModeIntra<34        -   If intraPredAngle>9, predModeIntra=predModeIntra+65, and            intra smoothing is performed;        -   Otherwise, predModeIntra=76,    -   If nTbH>nTbW and intraPredAngle>((32*nTbW/nTbH)+1) and        predModeIntra>34        -   If intraPredAngle>9, predModeIntra=predModeIntra−67, and            intra smoothing is performed;        -   Otherwise, predModeIntra=10.

In a fifth embodiment, the values of predModeIntra and wideAngle aremodified as follows:

-   -   If nTbW>nTbH and intraPredAngle>((32*nTbH/nTbW)+1) and        predModeIntra<34, and intra smoothing is performed;        -   If intraPredAngle>9, predModeIntra=predModeIntra+65;        -   Otherwise, predModeIntra=68−predModeIntra,    -   If nTbH>nTbW and intraPredAngle>((32*nTbW/nTbH)+1) and        predModeIntra>34, and intra smoothing is performed;        -   If intraPredAngle>9, predModeIntra=predModeIntra−67;        -   Otherwise, predModeIntra=68−predModeIntra.

The following describes further embodiments of the disclosure. Thedescribed methods may be used separately or combined in any order.Further, the embodiments may be implemented by processing circuitry(e.g., one or more processors or one or more integrated circuits). Inone example, the one or more processors execute a program that is storedin a non-transitory computer-readable medium.

In the following, if block width is equal to or larger than blockheight, the top row is called long side and the left column is calledthe short side. Otherwise, the top row is called the short side and leftcolumn is called the long side. The block width is indicated by nWidth(or nTbW) and the block height is indicated by nHeight (or nTbH).

When padding an array/buffer of N reference samples, it means thereference sample values are either filled by the neighboringreconstructed samples located at the associated position of referencesamples, or copied from reference samples that have already been filled,or derived from reference samples that have already been filled using apre-defined function (e.g., linear extrapolation).

Given a set of all available intra prediction directions, for aparticular block size W×H, it is constrained that only a pre-definedrange (or group, or number) of reference samples can be used for intraprediction, and any intra prediction direction S, which uses referencesamples outside the range of the pre-defined range (or group, or number)of reference samples, is mapped to a different intra predictiondirection X. Several embodiments follow.

In one embodiment, the mapped intra prediction direction X is includedin the set of all available intra prediction directions.

In another embodiment, the mapped intra prediction direction X does notuse reference samples outside the range of the pre-defined range (orgroup, or number) of reference samples.

In a further embodiment, the pre-defined range (or group, or number) ofreference samples include 2*W+N top neighboring reference samples and2*H+M left neighboring reference samples. Example values of M and Ninclude 1, 2, 3, 4, . . . 128.

In another embodiment, X is the diagonal intra prediction direction. Forexample, when 33 angular intra prediction modes are applied, S is mappedto 2 or 34 (as specified in above Table 5). For another example, when 65angular intra prediction modes are applied, S is mapped to 2 or 66. Foranother example, when W>H, X is mapped to mode 34 (when 33 angular intraprediction modes are applied) or 66 (when 65 angular intra predictionmodes are applied). For another example, when W<H, X is mapped to mode2.

In yet another embodiment, S=K−X, where K is a pre-defined constantvalue. Example values are 36 (when 33 angular intra prediction modes areapplied) and 68 (when 65 angular intra prediction modes are applied).

In one further embodiment, X is the widest intra prediction angle (withthe largest index or the smallest index) within the set of all availableintra prediction directions.

In another embodiment, X is a pre-defined intra prediction mode. Examplepre-defined intra prediction modes include: horizontal, vertical, planarand DC prediction modes.

In a further embodiment, S is mapped to one of the intra predictiondirection X of the set of all available intra prediction directions,however, the intra smoothing is applied differently. For example, ifintra smoothing is not applied on intra prediction direction X, after Sis mapped to intra prediction direction X, intra smoothing is applied.For another example, if intra smoothing is applied on intra predictiondirection X, after S is mapped to intra prediction direction X, intrasmoothing is not applied.

For rectangular blocks, whether intra smoothing is applied depends onblock width and/or height, instead of block area size. Severalembodiments using this concept are described below.

In one embodiment, when the Planar mode is used, whether intra smoothingis applied on the top neighboring reference samples depends on the blockwidth, and whether intra smoothing is applied on the left neighboringreference samples depends on the block height.

In another embodiment, when angular mode is used, whether intrasmoothing is applied on the top neighboring reference samples depends onthe block width, and whether intra smoothing is applied on the leftneighboring reference samples depends on the block height. In anexample, two tables (shown below) are used to decide whether intrasmoothing is applied. The following table 7 is used to decide whetherintra smoothing is applied on the left reference samples given the blockheight and intra mode ipred, when Abs(ipred—HOR_IDX) is larger thanintraVerDistThres[nTbH], intra smoothing is applied on the leftreference samples, otherwise, it is not applied. HOR_IDX indicates theintra mode index of horizontal intra prediction, it is 10 when 33angular modes are applied, it is 18 when 65 angular modes are applied.The threshold values in the following table are applied when 65 angularmodes are applied.

TABLE 7 nTbH = nTbH = nTbH = nTbH = nTbH = 4 8 16 32 64intraVerDistThres[nTbH] 20 14 2 0 20

Table 8 below is used to decide whether intra smoothing is applied onthe top reference samples given the block height and intra mode ipred,when Abs(ipred—VER_IDX) is larger than intraVerDistThres[nTbW], intrasmoothing is applied on the top reference samples, otherwise, it is notapplied. VER_IDX indicates the intra mode index of horizontal intraprediction, it is 26 when 33 angular modes are applied, and it is 50when 65 angular modes are applied. The threshold values in the followingtable are applied when 65 angular modes are applied.

TABLE 8 nTbW = nTbW = nTbW = nTbW = nTbW = 4 8 16 32 64intraHorDistThres[nTbW] 16 14 2 0 16

In another aspect of the embodiment, intra smoothing is applied for aspecific mode, color component or coding tool. Several embodiments aredescribed below.

In one embodiment, intra smoothing is never applied on Planar mode.

In another embodiment, intra smoothing is always applied on Planar mode.

In another embodiment, intra smoothing is always applied on DC mode.

In another embodiment, intra smoothing is applied for wide-angle intraprediction, for both luma and chroma components.

In another embodiment, intra smoothing is applied when a transform typeother than DCT-2 is used.

In another embodiment, intra smoothing never applied when a transformtype other than DCT-2 is used.

In another embodiment, intra smoothing is always applied when PDPC(Position-Dependent Prediction Combination) is used.

In another embodiment, intra smoothing is never applied when PDPC isused.

In another embodiment, intra smoothing is always applied when NSST(Non-Separable Secondary Transform) is used.

In another embodiment, intra smoothing is never applied when NSST isused.

In one embodiment, intra smoothing is never applied on CCLM(Cross-Component Linear Mode) mode.

In another embodiment, intra smoothing is always applied on CCLM mode.

PDPC may be applied to the angular modes which are close to the diagonaldirection of its block shape, where the diagonal direction is indicatedby the line connecting the top-right and bottom-left corners. Asindicated in FIG. 12 , the prediction angles (solid arrows) locatedwithin the top-left textured triangle area (120) are intra predictionangles within diagonal direction, and the prediction angles (dottedangles) 121 and 122 located outside the top-left textured triangle areaare intra prediction angle beyond diagonal direction. Furtherembodiments are described below.

In one embodiment, the number of modes for applying PDPC is the same fordifferent block shapes.

In another embodiment, the number of modes for applying PDPC isdifferent for square and non-square blocks.

In another embodiment, the number of modes for applying PDPC isdifferent for the bottom-left and top-right diagonal direction when thecurrent block is a non-square block.

In another embodiment, PDPC is not applied to bottom-left angles belowthe horizontal direction, i.e., modes 2˜17, when the width is largerthan the height.

In another embodiment, PDPC is not applied to top-right angles above thevertical directions, i.e., modes 51˜mode 66, when the height is largerthan the width.

The techniques and embodiments described above, can be implemented ascomputer software using computer-readable instructions and physicallystored in one or more computer-readable media. For example, FIG. 13shows a computer system 1300 suitable for implementing certainembodiments of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 13 for computer system 1300 are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 1300.

Computer system 1300 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 1301, mouse 1302, trackpad 1303, touch screen1310, data-glove (not shown), joystick 1305, microphone 1306, scanner1307, and camera 1308.

Computer system 1300 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 1310, data-glove (not shown), or joystick 1305, but therecan also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers 1309, headphones (notdepicted)), visual output devices (such as screens 1310 to include CRTscreens, LCD screens, plasma screens, OLED screens, each with or withouttouch-screen input capability, each with or without tactile feedbackcapability—some of which may be capable to output two dimensional visualoutput or more than three dimensional output through means such asstereographic output; virtual-reality glasses (not depicted),holographic displays and smoke tanks (not depicted)), and printers (notdepicted).

Computer system 1300 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW1320 with CD/DVD or the like media 1321, thumb-drive 1322, removablehard drive or solid state drive 1323, legacy magnetic media such as tapeand floppy disc (not depicted), specialized ROM/ASIC/PLD based devicessuch as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 1300 can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses 1349 (such as, for example USB ports of thecomputer system 1300); others are commonly integrated into the core ofthe computer system 1300 by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system 1300 can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 1340 of thecomputer system 1300.

The core 1340 call include one or more Central Processing Units (CPU)1341, Graphics Processing Units (GPU) 1342, specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)1343, hardware accelerators for certain tasks 1344, and so forth. Thesedevices, along with Read-only memory (ROM) 1345, Random-access memory1346, internal mass storage such as internal non-user accessible harddrives, SSDs, and the like 1347, may be connected through a system bus1348. In some computer systems, the system bus 1348 can be accessible inthe form of one or more physical plugs to enable extensions byadditional CPUs, GPU, and the like. The peripheral devices can beattached either directly to the core's system bus 1348, or through aperipheral bus 1349. Architectures for a peripheral bus include PCI,USB, and the like.

CPUs 1341, GPUs 1342, FPGAs 1343, and accelerators 1344 can executecertain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM1345 or RAM 1346. Transitional data can be also be stored in RAM 1346,whereas permanent data can be stored for example, in the internal massstorage 1347. Fast storage and retrieve to any of the memory devices canbe enabled through the use of cache memory, that can be closelyassociated with one or more CPU 1341, GPU 1342, mass storage 1347, ROM1345, RAM 1346, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 1300, and specifically the core 1340 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 1340 that are of non-transitorynature, such as core-internal mass storage 1347 or ROM 1345. Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core 1340. A computer-readablemedium can include one or more memory devices or chips, according toparticular needs. The software can cause the core 1340 and specificallythe processors therein (including CPU, GPU, FPGA, and the like) toexecute particular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 1346and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 1344), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

Appendix A: Acronyms

-   JEM: joint exploration model-   VVC: versatile video coding-   BMS: benchmark set-   MV: Motion Vector-   HEVC: High Efficiency Video Coding-   SEI: Supplementary Enhancement Information-   VUI: Video Usability Information-   GOPs: Groups of Pictures-   TUs: Transform Units,-   PUs: Prediction Units-   CTUs: Coding Tree Units-   CTBs: Coding Tree Blocks-   PBs: Prediction Blocks-   HRD: Hypothetical Reference Decoder-   SNR: Signal Noise Ratio-   CPUs: Central Processing Units-   GPUs: Graphics Processing Units-   CRT: Cathode Ray Tube-   LCD: Liquid-Crystal Display-   OLED: Organic Light-Emitting Diode-   CD: Compact Disc-   DVD: Digital Video Disc-   ROM: Read-Only Memory-   RAM: Random Access Memory-   ASIC: Application-Specific Integrated Circuit-   PLD: Programmable Logic Device-   LAN: Local Area Network-   GSM: Global System for Mobile communications-   LTE: Long-Term Evolution-   CANBus: Controller Area Network Bus-   USB: Universal Serial Bus-   PCI: Peripheral Component Interconnect-   FPGA: Field Programmable Gate Areas-   SSD: solid-state drive-   IC: Integrated Circuit-   CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in art will be able to devise numerous systems andmethods which, although not explicitly shown or described herein, embodythe principles of the disclosure and are thus within the spirit andscope thereof.

What is claimed is:
 1. A method for video decoding in a video decoder,the method comprising: decoding a coded video sequence to obtain anintra prediction mode that is a directional intra prediction mode andnot a planar intra prediction mode; determining an intra predictionangle, based on a predetermined plurality of intra prediction modes anda corresponding predetermined plurality of intra prediction angles, thedetermined intra prediction angle corresponding to the obtained intraprediction mode, the intra prediction angle being (i) beyond a bottomleft direction 45 degrees from horizontal diagonal mode; or (ii) beyonda top right direction 45 degrees from horizontal diagonal mode; andreconstructing at least one sample of a block based on the intraprediction angle that is determined to correspond to the obtained intraprediction mode.
 2. The method recited in claim 1, wherein the intraprediction angle corresponds to intraPredAngle and the intra predictionmode corresponds to predModeIntra, and a relationship between thepredetermined plurality of intra prediction modes and the correspondingpredetermined plurality of intra prediction angles is as follows:predModeIntra −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 2 3 4 5 6 7 8intraPredAngle 114 93 79 68 60 54 49 45 39 35 32 29 26 23 21 19 17predModeIntra 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25intraPredAngle 15 13 11  9 7 5 3 2 1 0 −1 −2 −3 −5 −7 −9 −11predModeIntra 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42intraPredAngle −13 −25 −17 −19 −21 −23 −26 −29 −32 −29 −26 −23 −21 −19−17 15 −13 predModeIntra 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 5859 intraPredAngle −11 −9 −7 −5 −3 −2 −1 0 1 2 3 5 7 9 11 13 15predModeIntra 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76intraPredAngle 17 19 21 23 26 29 32 35 39 45 49 54 60 68 79 93
 114.


3. The method recited in claim 2, wherein the reconstructing comprises:reconstructing the at least one sample of a non-square block based onthe relationship between predModeIntra and intraPredAngle.
 4. The methodrecited in claim 1, wherein the reconstructing comprises: reconstructingthe at least one sample of a non-square block based on a relationshipbetween the plurality of intra prediction modes and the plurality ofintra prediction angles.
 5. The method recited in claim 1, wherein anumber of the intra prediction modes that are beyond the bottom leftdirection 45 degrees from horizontal diagonal mode is ten; and a numberof the intra prediction modes that are beyond the top right direction 45degrees from horizontal diagonal mode is ten.
 6. The method recited inclaim 1, wherein a first plurality of the intra prediction modes thatare beyond the bottom left direction 45 degrees from horizontal diagonalmode have integer values in a range of −1 to −10; and a second pluralityof the intra prediction modes that are beyond the top right direction 45degrees from horizontal diagonal mode have integer values in a range of67 to
 76. 7. The method recited in claim 6, wherein the plurality ofintra prediction angles corresponding to each of the first and secondplurality of prediction modes are in a range of 35 to
 114. 8. The methodrecited in claim 1, wherein: the intra prediction modes go beyond mode 2of the HEVC (High Efficiency Video Coding) standard; and the intraprediction modes go beyond mode 34 of the HEVC standard.
 9. The methodrecited in claim 1, comprising: when a width W of the block is greaterthan a height H of the block, the intra prediction angle is greater than((32*H/W)+1), and the intra prediction mode is less 34, modifying theintra prediction mode by adding 65 when the intra prediction angle isless than 9, and setting the intra prediction mode to 66 when the intraprediction angle is at least
 9. 10. The method recited in claim 1,comprising: when a width W of the block is less than a height H of theblock, the intra prediction angle is greater than ((32*W/H)+1), and theintra prediction mode greater than 34, modifying the intra predictionmode by subtracting 67 when the intra prediction angle is greater than9, and setting the intra prediction mode to 2 when the intra predictionangle is 9 or less.
 11. The method recited in claim 1, comprising: whena width W of the block is greater than a height H of the block, theintra prediction angle is greater than ((32*H/W)+1), and the intraprediction mode is less than 34, modifying the intra prediction mode byadding 65 when the intra prediction angle is less than 9, and modifyingthe intra prediction mode by subtracting the intra prediction mode from68 when the intra prediction angle is at least
 9. 12. The method recitedin claim 1, comprising: when a width W of the block is less than aheight H of the block, the intra prediction angle is greater than((32*W/H)+1), and the intra prediction mode is greater than 34,modifying the intra prediction mode by subtracting 67 when the intraprediction angle is greater than 9, and modifying the intra predictionmode by subtracting the intra prediction mode from 68 when the intraprediction angle is 9 or less.
 13. The method recited in claim 1,comprising: when a width W of the block is greater than a height H ofthe block, the intra prediction angle is greater than ((32*H/W)+1), andthe intra prediction mode is less than 34, modifying the intraprediction mode by adding 65 when the intra prediction angle is lessthan 9, and setting the intra prediction mode to 76 when the intraprediction angle is at least
 9. 14. The method recited in claim 1,comprising: when a width W of the block is less than a height H of theblock, the intra prediction angle is greater than ((32*W/H)+1), and theintra prediction mode is greater than 34, modifying the intra predictionmode by subtracting 67 when the intra prediction angle is greater than9, and setting the intra prediction mode to −10 when the intraprediction angle is 9 or less.
 15. The method of claim 1, wherein theplurality of intra prediction modes go beyond mode 34 of the HEVCstandard.
 16. A video decoder for video decoding, comprising: processingcircuitry configured to: decode a coded video sequence to obtain anintra prediction mode that is a directional intra prediction mode andnot a planar intra prediction mode; determine an intra prediction angle,based on a predetermined plurality of intra prediction modes and acorresponding predetermined plurality of intra prediction angles thedetermined intra prediction angle corresponding to the obtained intraprediction mode , the intra prediction angle being (i) beyond a bottomleft direction 45 degrees from horizontal diagonal mode, or (ii) beyonda top right direction 45 degrees from horizontal diagonal mode; andreconstruct at least one sample of a block based on the intra predictionangle that is determined to correspond to the obtained intra predictionmode.
 17. The video decoder recited in claim 16, wherein the intraprediction angle corresponds to intraPredAngle and the intra predictionmode corresponds to predModeIntra, and a relationship between thepredetermined plurality of intra prediction modes and the correspondingpredetermined plurality of intra prediction angles is as follows:preModeIntra −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 2 3 4 5 6 7 8 intraPredAngle114 93 79 68 60 54 49 45 39 35 32 29 26 23 21 19 17 predModeIntra 9 1911 12 13 14 15 16 17 18 19 20 21 22 23 24 25 intraPredAngle 15 13 11  97 5 3 2 1 0 −1 −2 −3 −5 −7 −9 −11 preModeIntra 26 27 28 29 30 31 32 3334 35 36 37 38 39 40 41 42 intraPredAngle −13 −25 −17 −19 −21 −23 −26−29 −32 −29 −26 −23 −21 −19 −17 −15 −13 preModeIntra 43 44 45 46 47 4849 50 51 52 53 54 55 56 57 58 59 intraPredAngle −11 −9 −7 −5 −3 −2 −1 01 2 3 5 7 9 11 13 15 preModeIntra 60 61 62 63 64 65 66 67 68 69 70 71 7273 74 75 76 intraPredAngle 17 19 21 23 26 29 32 35 39 45 49 54 60 68 7993
 114.


18. The video decoder recited in claim 17, wherein the processingcircuitry is configured to reconstruct the at least one sample of anon-square block based on the relationship between predModeIntra andintraPredAngle.
 19. The video decoder recited in claim 16, wherein theprocessing circuitry is configured to reconstruct the at least onesample of a non-square block based on a relationship between theplurality of intra prediction modes and the plurality of intraprediction angles.
 20. The video decoder recited in claim 16, wherein anumber of the intra angle prediction modes that are beyond the bottomleft direction 45 degrees from horizontal diagonal mode is ten; and anumber of the intra angle prediction modes that are beyond the top rightdirection 45 degrees from horizontal diagonal mode is ten.
 21. The videodecoder recited in claim 16, wherein a first plurality of the intraprediction modes have integer values in a range of −1 to −10; and asecond plurality of the intra prediction modes have integer values in arange of 67 to
 76. 22. The video decoder recited in claim 21, whereinthe plurality of intra prediction angles corresponding to each of thefirst and second plurality of prediction modes are in a range of 35 to114.
 23. The video decoder recited in claim 16, wherein: the intraprediction modes go beyond mode 2 of the HEVC (High Efficiency VideoCoding) standard; and the intra prediction modes go beyond mode 34 ofthe HEVC standard.
 24. A non-transitory computer-readable medium storinginstructions which when executed by a computer for video decoding causethe computer to perform: decoding a coded video sequence to obtain anintra prediction mode that is a directional intra prediction mode andnot a planar intra prediction mode; determining an intra predictionangle, based on a predetermined plurality of intra prediction modes anda corresponding predetermined plurality of intra prediction angles, thedetermined intra prediction angle corresponding to the obtained intraprediction mode, the intra prediction angle being (i) beyond a bottomleft direction 45 degrees from horizontal diagonal mode, or (ii) beyonda top right direction 45 degrees from horizontal diagonal mode; andreconstructing at least one sample of a block based on the intraprediction angle that is determined to correspond to the obtained intraprediction mode.
 25. The medium recited in claim 24, wherein the intraprediction angle corresponds to intraPredAngle and the intra predictionmode corresponds to predModeIntra, and a relationship between thepredetermined plurality of intra prediction modes and the correspondingpredetermined plurality of intra prediction angles is as follows:preModeIntra −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 2 3 4 5 6 7 8 intraPredAngle114 93 79 68 60 54 49 45 39 35 32 29 26 23 21 19 17 predModeIntra 9 1911 12 13 14 15 16 17 18 19 20 21 22 23 24 25 intraPredAngle 15 13 11  97 5 3 2 1 0 −1 −2 −3 −5 −7 −9 −11 preModeIntra 26 27 28 29 30 31 32 3334 35 36 37 38 39 40 41 42 intraPredAngle −13 −25 −17 −19 −21 −23 −26−29 −32 −29 −26 −23 −21 −19 −17 −15 −13 preModeIntra 43 44 45 46 47 4849 50 51 52 53 54 55 56 57 58 59 intraPredAngle −11 −9 −7 −5 −3 −2 −1 01 2 3 5 7 9 11 13 15 preModeIntra 60 61 62 63 64 65 66 67 68 69 70 71 7273 74 75 76 intraPredAngle 17 19 21 23 26 29 32 35 39 45 49 54 60 68 7993 114.